Rocky Mountain Spotted Fever
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Rocky Mountain Spotted Fever


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Rocky Mountain spotted fever (RMSF) is a severe and potentially fatal disease spread by ticks. Although first recognized in the Rocky Mountain states, RMSF is found in practically all states in the United States.


RMSF is caused by the bacterium rickettsia rickettsii , which is carried by the American dog tick and the Rocky Mountain wood tick. When an infected tick bites a human, the disease is transmitted through the skin into the bloodstream. The bacteria multiply inside cells of the inner lining of small arteries causing inflammation, or vasculitis.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

  • Sex: male
  • Age: children and young adults
  • Exposure to tick-infested areas
  • Contact with pets that roam in tick-infested areas
  • Being outdoors often during the months of April to September
  • Residence in or visits to states where RMSF occurs most commonly; these include, but are not limited, to:
    • Arkansas
    • Georgia
    • Kentucky
    • North and South Carolina
    • Oklahoma
    • Tennessee
    • Virginia


Usually, the first symptom of RMSF is a sudden high fever that may occur within 1 to 14 days after a tick bite. Other symptoms may include:

  • Nausea
  • Vomiting
  • Muscle pain
  • Lack of appetite
  • Severe headache

Later signs may include:

  • Rash
  • Abdominal pain
  • Joint pain
  • Diarrhea
  • Cough
  • Irritability
  • Insomnia
  • Lethargy
  • Confusion
  • Delirium or, in severe cases, coma
  • Enlarged liver, spleen, and lymph nodes
  • In severe cases, low blood pressure or shock

Immune System Including Spleen and Lymph Nodes

Immune system

© 2008 Nucleus Medical Art, Inc.


The doctor will ask about your symptoms and medical history and perform a physical exam. RMSF can be difficult to diagnose because it resembles other diseases. Three indicators that your doctor will look for are:

  • Fever
  • Rash (may not be present early)
  • History of a tick bite (sometimes you may not have noticed)

Blood tests may be done to confirm the diagnosis, but treatment is often started based on a best guess basis. Sometimes doctors forget to think of RMSF when adults or children have only high fever.

Especially if you have been outdoors around ticks, ask your doctor, “Could I (or my child) have Rocky Mountain spotted fever?" That simple question may save a life.


RMSF is treated with antibiotics. It is important to start this treatment early. The most commonly used antibiotics are doxycycline and tetracycline .


The best way to prevent RMSF is to limit your exposure to ticks. If you live in an area that is prone to ticks, take the following precautions:

  • Wear light-colored clothing so ticks are more visible.
  • Tuck pant legs inside socks so ticks cannot crawl up under your pants.
  • Apply insect repellents containing DEET (applied to exposed skin) or permethrin (applied to clothing).
    • For young children, DEET should be avoided or used sparingly. Carefully follow the directions on the label.
  • Carefully check your entire body for ticks after returning from outdoor areas.
  • Check pets for ticks.


Centers for Disease Control and Prevention (CDC)

National Library of Medicine


Canadian Family Physician

Public Health Agency of Canada


Bratton RL, Corey GR. Tick-borne disease. Am Fam Physician . 2005;71(12):2323.

Rocky Mountain spotted fever. DynaMed website. Available at: . Accessed October 14, 2005.

Tick-borne diseases: Rocky Mountain Spotted Fever. eMedicine Journal . 2001 Jan 26.

Last reviewed December 2007 by David L. Horn, MD, FACP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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